I was not able to find much info on Diamondbacks. I bought an Apex of unknown vintage and wanted to know the same thing. I ended up looking at the Shimano date codes. They were all late '92 so I figure I have a 1993 Apex. The components description on bikepedia is a match for that year as well. Mine says "Diamond Back" with two words on the downtube. I understand later it changed to one word like on your bike. That should help get you closer anyway.
BikePedia
Date of Manufacture of Bicycle Components can be used to date a bike: component dating